Sheathed-wire terminal.



I. T. H.l DEMPSTER.

SHEATHED wmf TERMm/u.

APPLICATION FILED OCT. 2Q. 1912.'

Patenfed Mar. 28, 1916.

Witnesses Inventor-z' l John THD m tsr; b5 M His I Mttor-Ijjsg UNITED STATES PATENT OFFICE.

JOHN T. H. DEMISTER, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SHEATHED-WIRE TERMINAL.

Specication of Letters Patent.

Patented Mar. 28, 1916.

Application led October 29, 1912. Serial No. 728,341.

To all whom it may concern:

Be it known that I, JOHN T. H. DEM?- s'rER, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Sheathed- Wire Terminals, of which the following is a specification.

My invention relates to electric terminals adapted for use in connection with metal sheathed or armored wire.

As is well known armored wire consists of an inner wire, an outer sheath and insulating material such as lime or silica 'separating the two. This wire is used for many purposes for some of which, for instance, as resistance wire in rheostats and heaters, the inner wire must be small in cross-section in order 'to have the requisite resistance. On the other hand the external conductors leading to the resistance wire must for thesake of economy have a fairly low resistance and must therefore be comparatively large in cross section. If it were attempted to connect the resistance wire to the external conductors without providing means such as are comprised by my invention, diiculties would arise by reason of the fact that the union between the two wires would be exposed in practice to the oxidizing action of the atmosphere at high temperatures, and also to considerable bending stresses. The result would be that the resistance wire would be burned away or broken at the point of union.

The object of my invention is to provide a terminal which will obviate these difficulties and at the same time preserve an effective insulation between the resistance wire and adjacent conductors so as to prevent a short circuit.

In carrying out my invention I strip the sheath and insulation from the wire for a short distance from the end thereof. Tothe exposed end of the resistance wire I unite the larger size conductor-for the external circuit by brazing or welding or other well known process. I surround the resistance wire and the terminal pin or larger conductor at the point of union and for a short distance on either side thereofwith compressible electrical insulation which may be of the same nature as the insulation contained in the sheathed wire. I prefer that the said insulation be contained within a metal or other rigid cup which is firmly connected to the sheath of the resistance wire. In connection with these parts I pro-` vide means for applyingl and maintaining pressure upon the insulation so as to retain the 'same securely in 4place and the more effectively to exclude the atmosphere from the j 0int, and to include the heat conducting propertiesof the insulating material. I also provide means for maintaining rigidly the position of the terminal pin or external conductor and, in case the cup is of conducting material for effectively insulating the said pin from the said cup.

I have shown my invention embodied in a terminal suitable for use in connection with a heating device such as a flat-iron. The connection with the external circuit in the case of a flat-iron is ordinarily made by means of a plug which contains a pair of sockets to receive a pair of terminal pins which are attached to the iron. These terminal pins must be very effectively insulated from each other to prevent short circuit and must also be very rigidly held in position. Moreover they must be of such material and dimensions that they will have considerable strength and wear resisting properties. This is essential because of the fact that while the flat-iron is in use the circuit is often broken by detaching the plug. The use of my invention in connection with a flat-iron or similar devices will effectively fulfil the above stated requirements.

My invention will be more clearly understood. by referring to the accompanying drawing in which is shown a vertical section of a terminal embodying my invention.

As shown in the drawing 10 is the terminal portion of a metal sheathed wire unit. It comprises a metal sheath 11, the inner resistance conductor 12 andthe insulation lseparating the same. the latter being comminuted and preferably in the form of a powder. The sheath l1 may be of iron or steel or any metal having good wearing quality. The conductor 12 may be any good electrical resistance material and 13 may be lime, silica, or any other good insulation. The terminal embodying my invention comprises a cup 14 preferably of metal such as iron or steel which has a stem 15 and may also have a flange 'i6 at the base of the same so that this portion of the terminal may be secured by casting or otherwise to the device in connection with which it is to be used. The stem 15 is bored to receive the end of the sheathed wire 10 and is connected to the sheath 11 of the same as by the screw connection 17. The end of the resistance wire l2 is exposed for a short distance and extends into the bottom of the cup 14. The terminal pin 18 which may be brass or other good conducting material and of such dimensions as to be suiliciently strong to resist wear extends into the cup 14 and preferably almost to the bottom thereof. An electrical connection between the terminal 18 and the resistance wire 12 is preferably made through an intermediate conductor 19 which may be of copper, brass or other good conducting material and which extends through a bore in the terminal pin 18. The end 20 of the said conductor may be connected withthe resistance wire 12 by brazing or welding. An electrical connection is also made by brazing or otherwise between the conductor 19 and the terminal pin at some easily accessible point, preferably at 21. Around the conductor 19 and the resistance wire 12 at the point of union thereof is packed insulation 22 which may be any compressible insulation and is preferably lime or other material similar to that contained in the metal sheathed wire. The inner end of the terminal pin 18 is preferl ably enlarged at 23 so as to increase the bearing area thereof, and also to form a shoulder for the insulating bushing 24 which extends a short distance above the top of the cup. The cup 14 is externally threaded to receive an internally threaded cap 25.

In assembling the above described parts the conductor 19 is welded or brazed to the resistance wire 12 near the bottom of the cup 14. A certain amount of the insulation 22 is packed adjacent to the point of union.

The terminal pin 18 is then inserted in the cup, Ithe conductor 19 being passed through the same. The insulating bushing 24 is then placed in position on the shoulder of the terminal pin and the cup 25 is passed over the terminal pin and screwed down until it forces the bushing and the terminal pin firmly against the insulation so as to compress it around the conductor 19 and so that the parts will be held firmly in their proper positions. The conductor 19 may then be electrically connected at 21 as by brazing, welding or other suitable process to the terminal pin 18.

It will be seen that I have provided a terminal in which the resistance wire is effectively insulated, in which the connection between the said wire and external circuit is effectively protected against the oxidizing action of the atmosphere and which is also reinforced so as to protect the same against bending stresses. The construction is such that the parts are held firmly in place and will stand considerable rough usage without disarrangement. Moreover the terminal may be easily disassembled by breaking the connection 21 and unscrewing the cap 25.

Various modifications of the above described structure will readily suggest themselves to those skilled in the art and are to be considered as coming within the scope of my invention as set forth in the following claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

l. A terminal for insulated armored wire consisting of a conductor electrically connected with the said armored wire, comminuted refractory electric insulation surrounding the said conductor and the said wire at the point of union, and means comprising a receptacle for the insulation for holding the said parts in place and maintaining the insulating material under pressure.

2. The combination with a metal sheathed and insulated wire, of an external conductor of larger cross section than said wire connected to the same, a body of comminuted refractory insulation surrounding a portion of said wire and said external conductor, and means comprising a receptacle for the insulation for maintaining said insulation under pressure and said conductor rigidly in place.

3. The combination of an insulated sheathed wire and a terminal for the same consisting of a conductor of considerably larger diameter than the sheathed Wire, means for electrically connecting the said conductor to the said sheathed Wire, a compressible comminuted electrical insulation surrounding the aforesaid elements at the point of lunion of the same and means for maintaining the position of the conductor with respect to vsaid wire and for maintaining pressure upon said insulating material.

4. The combination of a cup having a hollow stem extending from the bottom thereof, an armored insulated wire extending through the said stem into the the said cup and having the end portion thereof exposed, a conductor of greater-diameter than said armored wire extending through the top of said cup and connected to the exposed end of the said armored wire, comminuted electric insulation packed around the point of union of said wire and said conductor and means for maintaining pressure upon said insulation and for holding the parts rigidly in place.

5. A terminal for metal sheathed Wire comprising a cup the bottom of which is apertured to receive the end of said sheathed wire, a tubular terminal pin extending into lthe opposite end. of said cup, a conductor of larger cross section than the core of the bottom of sheathed wire connecting the same with the terminal pin and extending into the latter, insulation between the said cup and the contained parts and means for maintaining pressure upon said insulation and for maintaining the position of the said parts with reference to said cup.

6. The combination of a sheathed resistance wire having a comminuted insulating material between the resistance wire and the sheath, a terminal of greater cross-section than said resistance wire and electrically connected thereto, a body of insulating material of the same character as that around the resistance wire surrounding the joint between the resistance wire and the terminal, and means for retaining said insulating material in position and for subjecting the same to pressure.

7. The combination of a resistance element for electric heaters and the like, comprising a high resistance core wire, a metal tube surrounding the same, a lling of heat refractory insulating powder between the two, and a terminal for the wire comprising a receptacle in .which the end of the sheathed wire is received, a terminal conductor of higher conductivity than the core wire joined to the end thereof, the space within the receptacle surrounding the joint being filled with a refractory insulating powder, and means for compressing said powder.

8. The combination of a resistance element for electric heaters and the like, comprising a high resistance core wire, a metal tubejsurrounding the same, a filling of heat refractory insulating powder between the two, and a terminal for the wire comprising a receptacle in which the end of the sheathed wire is received, a terminal conductor of higher conductivity than the core wire joined to the end thereof, the space within the receptacle surrounding the joint -being lilled with a refractory insulating powder', and means for closing said receptacle and placing the material therein under compression.

9. The combination of a resistance element for electric heaters and the like comprising a high resistance core wire, a metal tube surrounding the same, a illing of heat refractory insulating powder between the two, and a terminal for the wire comprising a metallic receptacle in which the end of the sheathed wire is received, a conductor of higher conductivity than the core wire joined to the end thereof, the space within the receptacle surrounding the joint being filled with a refractory insulating powder, means for insulating the terminal conductor from the metallic receptacle, and means for closing said receptacle and placing the insulating powder' under compression.

In witness whereof, I have hereunto set my hand this 28th day of October, 1912.

JOHN T. H. DEMPSTER.

Witnesses:

HELEN ORFORD, MARGARET E. WOOLLEY, 

